Spock knew he had to give his answer soon, but he was still unsure. His intellect kept telling him to take it, and he was leaning towards that option. Logically, he knew he was qualified for the position and the opportunities it presented for study, both scientific and cultural, were substantial. He compared this position with the Enterprise. Life with the Medusans would be quieter, calmer; with few dangers and unknowns. Life on the Enterprise was rarely quiet or peaceful; they lived in a constant state of uncertainty about what danger they would find next, and Spock was no longer sure if he wanted to remain in that environment. In addition, with the Medusans, he would no longer be the sole Vulcan on a ship full of humans. He would be the only Vulcan among the Medusans, at least at the start, but from everything he had heard, the Medusans were culturally and temperamentally similar to Vulcans. It would certainly be easier on him, not being around humans so much. Spock knew his controls were weaker than they should have been; he had given in far too much to human influence and that didn't even count the number of times the number of times he had had to lower them completely to use his telepathic ability to save himself or the crew. After constantly dealing with the emotional atmosphere of over four hundred humans, the Medusans and their world would be restful.
And yet, Spock also knew that the opportunities the Enterprise and Starfleet presented were just as great. He had made more discoveries in his time as Science Officer than he could study on any posting planetside. He had also met more cultures, opened up more relations that led to cultural study and Federation diplomacy on the Enterprise than he could in any liaison position. Thinking back on these events, Spock had a definite satisfaction in his accomplishments. Even in their less peaceful encounters with the Klingons and the Romulans, Spock knew that the Enterprise's actions protected the Federation from attack, another satisfying result. That was another plus for the Medusans; they had no war, where Spock was forced on the Enterprise to be involved, even tangentially, in violence that he found personally repugnant. But there was something about being the first to discover something, to land on a new planet. Not for the recognition, but for the challenge of figuring out the possibilities. Finding his way through a new situation, testing new discoveries to see what answers they held to long-asked questions. Jim would have called it the "thrill of discovery." Spock knew that, as a scientist, it was the most intellectual stimulation one could have. Even in dangerous situations, there was something about trying to come up with a plan to make it out alive, doing the best you could with what you had. Spock had always thought of it as a challenge, testing his logic and intelligence against whatever the universe could throw at him. He knew he would have little of that challenge as the Medusan liaison, and any scientific discoveries would be second-hand, discovered by the Medusans first. Not challenging, but still fascinating. Surely, the benefit of their knowledge was the most important factor here, Spock asked himself. But the benefits of the Enterprise's mission were just as great, and had Spock been human, he would have sighed in frustration. Logic seemed to be no help here, as both choices had equally logical benefits, as well as compromises that would have to be made.
Very well. Spock dug a little deeper, searching for factors he might have missed. He wondered if he was ready to make such a large change to his life. He was used to the Enterprise, however much it was a human ship, and he was a creature of habit. The last time he'd made such a large change had been when he'd walked out of his parents' house and joined Starfleet twenty years before. Since then, he'd attended the Academy and served only aboard the Enterprise. Changing positions like this, essentially changing careers, was a big change. But, Spock thought, maybe it is time for a change. It is not logical to remain in one place too long, as it will affect future career prospects. He was just about to send in his acceptance, when he suddenly found himself flooded with memories.
The captain is seated across from him, a chess board on the table. They're discussing the latest book Jim has recommended to him and Jim is laughing.
Spock is in his quarters reading a scientific journal. He comes across an article he knows McCoy with disagree with and sends it to him. Minutes later, the doctor appears at his door, and they spend the rest of the night arguing about it over Vulcan spiced tea.
They are at a diplomatic function. Spock wanders alone through the guests; he's never understood small talk, until he sees Kirk cornered by Admiral Kettison and his latest pet project. Spock goes over and starts discussing soil erosion on Centauri Beta until the Admiral gets visibly bored and leaves. Kirk looks at him gratefully and starts to laugh.
A year ago, on Christmas Day, Spock has been on duty all day, allowing most of the crew to celebrate. He hasn't seen Kirk or McCoy all day and expects nothing more on returning to his cabin that evening. Instead, he finds an invitation to come to the captain's quarters. On arriving, Spock finds Jim and the doctor; they hand him a rare potted plant, direct from Vulcan and a travel case for his lyre, embossed with the Vulcan characters of his name. Spock is, for once, speechless, and Jim says, "I know it's not your holiday, but you didn't think we'd leave you alone on Christmas?"
A few months ago, Spock is looking for Captain Kirk, to give him a report, and finds him in the ship's pool. While they are talking, McCoy comes in, sneaks behind Spock and pushes him in the water. Kirk looks shocked and McCoy is laughing. Spock makes his way to the edge, and when McCoy takes pity on him and offers a hand to pull him up, Spock pulls him into the water instead. Kirk bursts out laughing and Spock decides it's almost worth getting soaked to see the shocked look on the doctor's face.
More and more of the memories surface; missions where they depended on each other, nights spent watching over each other in Sickbay, everything ranging from light banter to deep discussions, from McCoy's teasing to Kirk almost destroying his own career to get Spock to Vulcan. And ending with the resigned acceptance of his decision to leave on McCoy's face and the sad hope in Jim's eyes that his leaving wouldn't change everything. Spock knew, in that moment, however illogical the decision and however great the opportunities for learning from the Medusans were, someone else would have to take them. He could not.